The IEEE 802.3 standard defines Carrier Sense Multiple Access/Collision Detection (CSMA/CD) as its Media Access Control (MAC) protocol for Ethernet local area networks (LAN's). A station connected to an Ethernet LAN may be fixedly configured to communicate with other stations of the LAN in a single mode (e.g. 10BASE-T, 10BASE-T Full Duplex, 100BASE-TX, 100BASE-TX Full Duplex, and 100BASE-T4), or the communication mode of the station may be changeable to match the configuration of the other stations. In any case, the communication mode of a particular station must match the communication mode of another station before communication can take place between the two stations.
The proliferation of CSMA/CD-based LANs will spawn a new generation of multi-function hubs and nodes. The trend among hub vendors towards "virtual networks" wherein ports can be switched between LANs will necessitate that, without an auto-negotiation solution such as is provided by the present invention, users and information services managers will face difficult configuration management problems in the future.
The necessity for providing in a station means for automatically detecting the communication capabilities of other stations in a network has been recognized. A method and apparatus for performing such automatic detection is the subject of copending patent application Ser. No. 08/146,729, filed and assigned to National Semiconductor Corporation, the assignee of the present application. As described in the copending application, each of two connected stations communicates to the other station, via Fast Link Pulses, its respective communication capabilities. When each station has detected the other stations capabilities, the stations each automatically change to a configuration which provides the highest common denominator of capabilities.
However, the technology of LAN's is evolving such that manufacturers of LAN's will be providing stations which will are reconfigurable to support any of multiple protocols.